Therre is now a considerable demand in the industrial field for technical fibers which are able to resist both high temperature, on the order of 450.degree. C., and the action of aggressive chemical products.
Some uses, particularly in the field of packings, also call for having elements resistant to high pressures, on the order of 400 bars.
At present, these packings are most often made from molded expanded graphite elements, but this is a burdensome solution. In addition, packings made of asbestos fibers cause problems of atmospheric pollution.